Add typesafe method to get generic bean by name with type reference

Fix GH-34687

Signed-off-by: Yanming Zhou <[email protected]>

Author: quaff

spring-beans/src/main/java/org/springframework/beans/factory/BeanFactory.java

@@ -16,6 +16,8 @@
 
 package org.springframework.beans.factory;
 
+import java.lang.reflect.Type;
+
 import org.jspecify.annotations.Nullable;
 
 import org.springframework.beans.BeansException;
@@ -100,6 +102,7 @@
  * @author Rod Johnson
  * @author Juergen Hoeller
  * @author Chris Beams
+ * @author Yanming Zhou
  * @since 13 April 2001
  * @see BeanNameAware#setBeanName
  * @see BeanClassLoaderAware#setBeanClassLoader
@@ -175,6 +178,37 @@ public interface BeanFactory {
 	 */
 	<T> T getBean(String name, Class<T> requiredType) throws BeansException;
 
+	/**
+	 * Return an instance, which may be shared or independent, of the specified bean.
+	 * <p>Behaves the same as {@link #getBean(String)}, but provides a measure of type
+	 * safety by throwing a BeanNotOfRequiredTypeException if the bean is not of the
+	 * required type. This means that ClassCastException can't be thrown on casting
+	 * the result correctly, as can happen with {@link #getBean(String)}.
+	 * <p>Translates aliases back to the corresponding canonical bean name.
+	 * <p>Will ask the parent factory if the bean cannot be found in this factory instance.
+	 * @param name the name of the bean to retrieve
+	 * @param typeReference the reference to obtain type the bean must match
+	 * @return an instance of the bean.
+	 * Note that the return value will never be {@code null}. In case of a stub for
+	 * {@code null} from a factory method having been resolved for the requested bean, a
+	 * {@code BeanNotOfRequiredTypeException} against the NullBean stub will be raised.
+	 * Consider using {@link #getBeanProvider(Class)} for resolving optional dependencies.
+	 * @throws NoSuchBeanDefinitionException if there is no such bean definition
+	 * @throws BeanNotOfRequiredTypeException if the bean is not of the required type
+	 * @throws BeansException if the bean could not be created
+	 * @see #getBean(String, Class)
+	 * @since 7.0
+	 */
+	@SuppressWarnings("unchecked")
+	default <T> T getBean(String name, ParameterizedTypeReference<T> typeReference) throws BeansException {
+		Object bean = getBean(name);
+		Type requiredType = typeReference.getType();
+		if (!ResolvableType.forType(requiredType).isInstance(bean)) {
+			throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
+		}
+		return (T) bean;
+	}
+
 	/**
 	 * Return an instance, which may be shared or independent, of the specified bean.
 	 * <p>Allows for specifying explicit constructor arguments / factory method arguments,

spring-beans/src/main/java/org/springframework/beans/factory/BeanNotOfRequiredTypeException.java

@@ -16,6 +16,9 @@
 
 package org.springframework.beans.factory;
 
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+
 import org.springframework.beans.BeansException;
 import org.springframework.util.ClassUtils;
 
@@ -24,6 +27,7 @@
  *
  * @author Rod Johnson
  * @author Juergen Hoeller
+ * @author Yanming Zhou
  */
 @SuppressWarnings("serial")
 public class BeanNotOfRequiredTypeException extends BeansException {
@@ -37,6 +41,8 @@ public class BeanNotOfRequiredTypeException extends BeansException {
 	/** The offending type. */
 	private final Class<?> actualType;
 
+	/** The required generic type. */
+	private final Type requiredGenericType;
 
 	/**
 	 * Create a new BeanNotOfRequiredTypeException.
@@ -46,11 +52,32 @@ public class BeanNotOfRequiredTypeException extends BeansException {
 	 * the expected type
 	 */
 	public BeanNotOfRequiredTypeException(String beanName, Class<?> requiredType, Class<?> actualType) {
-		super("Bean named '" + beanName + "' is expected to be of type '" + ClassUtils.getQualifiedName(requiredType) +
+		this(beanName, (Type) requiredType, actualType);
+	}
+
+	/**
+	 * Create a new BeanNotOfRequiredTypeException.
+	 * @param beanName the name of the bean requested
+	 * @param requiredType the required type
+	 * @param actualType the actual type returned, which did not match
+	 * the expected type
+	 * @since 7.0
+	 */
+	public BeanNotOfRequiredTypeException(String beanName, Type requiredType, Class<?> actualType) {
+		super("Bean named '" + beanName + "' is expected to be of type '" + requiredType.getTypeName() +
 				"' but was actually of type '" + ClassUtils.getQualifiedName(actualType) + "'");
 		this.beanName = beanName;
-		this.requiredType = requiredType;
+		this.requiredGenericType = requiredType;
 		this.actualType = actualType;
+		if (requiredType instanceof Class<?> requiredClass) {
+			this.requiredType = requiredClass;
+		}
+		else if (requiredType instanceof ParameterizedType parameterizedType) {
+			this.requiredType = (Class<?>) parameterizedType.getRawType();
+		}
+		else {
+			throw new IllegalArgumentException(requiredType + " is not supported");
+		}
 	}
 
 
@@ -68,6 +95,14 @@ public Class<?> getRequiredType() {
 		return this.requiredType;
 	}
 
+	/**
+	 * Return the expected generic type for the bean.
+	 * @since 7.0
+	 */
+	public Type getRequiredGenericType() {
+		return this.requiredGenericType;
+	}
+
 	/**
 	 * Return the actual type of the instance found.
 	 */

spring-beans/src/main/kotlin/org/springframework/beans/factory/BeanFactoryExtensions.kt

@@ -24,21 +24,22 @@ import org.springframework.core.ResolvableType
  * This extension is not subject to type erasure and retains actual generic type arguments.
  *
  * @author Sebastien Deleuze
+ * @author Yanming Zhou
  * @since 5.0
  */
 inline fun <reified T : Any> BeanFactory.getBean(): T =
 		getBeanProvider<T>().getObject()
 
 /**
  * Extension for [BeanFactory.getBean] providing a `getBean<Foo>("foo")` variant.
- * Like the original Java method, this extension is subject to type erasure.
+ * This extension is not subject to type erasure and retains actual generic type arguments.
  *
  * @see BeanFactory.getBean(String, Class<T>)
  * @author Sebastien Deleuze
  * @since 5.0
  */
 inline fun <reified T : Any> BeanFactory.getBean(name: String): T =
-		getBean(name, T::class.java)
+		getBean(name, (object : ParameterizedTypeReference<T>() {}))
 
 /**
  * Extension for [BeanFactory.getBean] providing a `getBean<Foo>(arg1, arg2)` variant.

spring-beans/src/test/java/org/springframework/beans/factory/DefaultListableBeanFactoryTests.java

@@ -79,6 +79,7 @@
 import org.springframework.beans.testfixture.beans.factory.DummyFactory;
 import org.springframework.core.MethodParameter;
 import org.springframework.core.Ordered;
+import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.annotation.AnnotationAwareOrderComparator;
 import org.springframework.core.annotation.Order;
@@ -1682,6 +1683,29 @@ void getBeanByTypeWithAmbiguity() {
 				lbf.getBean(TestBean.class));
 	}
 
+	@Test
+	void getBeanByNameWithTypeReference() {
+		RootBeanDefinition bd1 = new RootBeanDefinition(StringTemplate.class);
+		RootBeanDefinition bd2 = new RootBeanDefinition(NumberTemplate.class);
+		lbf.registerBeanDefinition("bd1", bd1);
+		lbf.registerBeanDefinition("bd2", bd2);
+
+		Template<String> stringTemplate = lbf.getBean("bd1", new ParameterizedTypeReference<>() {});
+		Template<Number> numberTemplate = lbf.getBean("bd2", new ParameterizedTypeReference<>() {});
+
+		assertThat(stringTemplate).isInstanceOf(StringTemplate.class);
+		assertThat(numberTemplate).isInstanceOf(NumberTemplate.class);
+
+		assertThatExceptionOfType(BeanNotOfRequiredTypeException.class)
+				.isThrownBy(() -> lbf.getBean("bd2", new ParameterizedTypeReference<Template<String>>() {}))
+				.satisfies(ex -> {
+					assertThat(ex.getBeanName()).isEqualTo("bd2");
+					assertThat(ex.getRequiredType()).isEqualTo(Template.class);
+					assertThat(ex.getActualType()).isEqualTo(NumberTemplate.class);
+					assertThat(ex.getRequiredGenericType().toString()).endsWith("Template<java.lang.String>");
+				});
+	}
+
 	@Test
 	void getBeanByTypeWithPrimary() {
 		RootBeanDefinition bd1 = new RootBeanDefinition(TestBean.class);
@@ -3872,4 +3896,16 @@ public Class<?> getObjectType() {
 		}
 	}
 
+	private static class Template<T> {
+
+	}
+
+	private static class StringTemplate extends Template<String> {
+
+	}
+
+	private static class NumberTemplate extends Template<Number> {
+
+	}
+
 }

spring-beans/src/test/kotlin/org/springframework/beans/factory/BeanFactoryExtensionsTests.kt

@@ -21,6 +21,7 @@ import io.mockk.mockk
 import io.mockk.verify
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.jupiter.api.Test
+import org.springframework.core.ParameterizedTypeReference
 import org.springframework.core.ResolvableType
 
 /**
@@ -53,7 +54,16 @@ class BeanFactoryExtensionsTests {
 	fun `getBean with String and reified type parameters`() {
 		val name = "foo"
 		bf.getBean<Foo>(name)
-		verify { bf.getBean(name, Foo::class.java) }
+		verify { bf.getBean(name, ofType<ParameterizedTypeReference<Foo>>()) }
+	}
+
+	@Test
+	fun `getBean with String and reified generic type parameters`() {
+		val name = "foo"
+		val foo = listOf(Foo())
+		every { bf.getBean(name, ofType<ParameterizedTypeReference<List<Foo>>>()) } returns foo
+		assertThat(bf.getBean<List<Foo>>("foo")).isSameAs(foo)
+		verify { bf.getBean(name, ofType<ParameterizedTypeReference<List<Foo>>>()) }
 	}
 
 	@Test